Reproductive studies on Volutes of the South West Atlantic (Neogastropoda: Volutidae).

PENCHASZADEH, PABLO E.; ARRIGHETTI, FLORENCIA; BIGATTI, GREGORIO; CLEDÓN MAXIMILIANO; GIMÉNEZ, JULIANA; CARLOS SANCHEZ ANTELO.

ANTWERP, BELGIUM

Congreso; WORLD CONGRESS OF MALACOLOGY. ANTWERP, BELGIUM, 15-20 JULY 2007.; 2007

UNITAS MALACOLOGICA

Reproductive patterns and season of five volutid neogastropods have been studied: Adelomelon brasiliana (Lamarck, 1811), Zidona dufresnei (Donovan,1823) and Adelomelon beckii (Broderip, 1836) from the subfamily Zidoninae in Mar del Plata; Odontocymbiola magellanica (Gmelin, 1791) and Adelomelon ancilla (Lightfoot, 1786) from north Patagonia (subfamilies Odontocymbiolinae and Zidoninae respectively). Volutids spawn large egg capsules containing few eggs. The embryos develop and grow for a period of up to three months; eggs ranged between 90 to 300 ìm in diameter, feed extravitelline food contained in the intracapsular fluid; no nurse eggs occur and they hatch as crawling juveniles exceeding 1 cm in shell length. The reproductive season of Adelomelon brasiliana extended from September to April. This is the only volutid known to lay free egg capsules. Gonad development in Zidona dufresnei reveals a reproductive season from October to March. Size at which 50% of the population was mature was 15.7 cm in females and 15.0 cm in males. Preliminary studies of Adelomelon beckii  showed the spawning season from August to January. Egg capsules are attached to hard substrate, is semi-spherical, with a diameter of 50 mm and 35 mm high and the number of embryos varies from 7 to 9. Odontocymbiola magellanica spawn white, spherical, calcareous egg capsules attached to hard flat surfaces. Major oviposition events occurred from July to December, characterized by females’ aggregation. Male individuals reach maturity at 80 mm and females mature at  90 mm (7 and 8 years of age respectively). Oviposition in Adelomelon ancilla  occur mainly from June to December. Minimum shell length of a females laying egg capsules was 114 mm. In the patagonic species oviposition was coincident with increasing of photoperiod from winter to summer solstices and not apparently by increasing of water temperature as observed in the species from Mar del Plata.